1. Field of the Invention
The present invention relates to seat tilt adjustment mechanisms having constantly engaged gears.
2. Background Art
Vehicle seats normally include a seat base and a seat back. Adjustment mechanisms are provided for vehicle seats that allow the seats to be positioned to accommodate different body types and the personal comfort of seat occupants. Adjustment mechanisms are provided for fore-and-aft positioning, lumbar support, seat height and the angular orientation of the seat back relative to the seat base. Adjustment mechanisms that adjust the angular orientation of the seat back relative to the seat base may be referred to as seat tilt adjusters.
Power seat adjusters are generally of the continuous engagement type in which gears having offset centers of rotation are constantly engaged. Power seat adjusters are driven by a bi-directional motor that provides torque to the seat adjuster to increase or decrease the angle at which the seat back is oriented relative to the seat base. Seat tilt adjusters must meet or exceed performance specifications and performance requirements of customers. Power seat adjusters must be manufactured to close tolerances to assure acceptable performance. Once the angular orientation of the seat back is adjusted, the seat back may be subject to loads or vibrations that cause the seat to chuck or vibrate. The term “chuck” refers to free movement of the seat back after the seat back position is established. Chucking is generally undesirable and many attempts have been made to eliminate this phenomenon. Seat tilt adjusters that are designed to eliminate chucking require manufacturing the parts of the seat tilt adjuster to very close tolerances. Failure to meet the tolerances required for such parts may lead to inconsistent results, unacceptable levels of scrap, and other manufacturing problems.
The present invention is directed to overcoming the above problems as summarized below.